1. Field of the Invention
This invention relates to a method and device for manufacturing a semiconductor sensor including a silicon wafer and a glass substrate. More specifically, when a silicon wafer having a diaphragm is bonded with a glass substrate through an anodic bonding process, the glass substrate contains a dielectric material and a recess or a cavity so as to avoid a bond from occurring between the glass substrate and the silicon wafer.
2. Related Art
In FIG. 6, an anodic-bonding process has the following steps. A silicon wafer 201 having a smooth surface 201a and a diaphragm 201b is bonded to a glass substrate 202 (for example, pyrex glass). After that, a unit containing the silicon wafer 201 and the glass substrate 202 is heated in the range of 300.degree. C.-400.degree. C. by a hot plate 204. Under this condition, when a negative voltage within 500-1000 V is applied to the glass substrate 202 by a negative electrode 203, a large electrostatic attracting force is generated between the silicon wafer 201 and the glass substrate 202 so that the chemical bonding occurs between the silicon wafer 201 and the glass substrate 202 at a boundary surface therebetween. However, in the step of applying a voltage to the glass substrate 202, the diaphragm 201b is undesirably bonded to the glass substrate 202 due to the large electrostatic attracting force generated between the silicon wafer 201 and the glass substrate 202.
In view of this problem, in Unexamined Japanese Utility Model Application No. Sho. 3-88137, for example, an oxide layer is formed on both sides of the diaphragm so as to prevent bonding between the diaphragm 201b and the glass substrate 202. However, if this structure is employed, it is difficult to ensure sufficient sensitivity characteristics of the sensor.